The invention relates to a device for shaping a workpiece comprising at least one first and one second component between which the workpiece to be shaped can be molded while being heated.
A device for shaping a workpiece expands uniformly in all directions under the influence of the temperature during curing of the workpiece. If the workpiece is produced from a composite material, in particular a fiber reinforced composite, forces or relative displacements can act on the workpiece that impair the quality of the workpiece. Such an impairment can be caused, for example, by fiber warpage. Moreover, the uniform thermal expansion of the components of the device results, in some cases, in the dimensional stability of the workpiece to be produced lying outside of the specified tolerances.
Accordingly, exemplary embodiments of the present invention are directed to a device for shaping a workpiece by means of which device, the quality of the produced workpieces can be improved.
Exemplary embodiments of the present invention provide a device for shaping a workpiece comprising a first and a second component between which the workpiece to be shaped can be molded under the effect of heat. The device is arranged so the its design and the material properties of the first and/or the second component are selected such that the thermal expansion of the component is different in different directions.
By providing a device with directed thermal expansion, it is possible during production to mold workpieces, which are formed from fiber reinforced composites, in a certain direction. Accordingly, forces or relative displacements in a different undesired direction that would cause an impairment of the workpiece to be manufactured can be eliminated. It is possible to avoid fiber bonding in the workpiece to be manufactured. The result of a workpiece manufactured in a device according to the invention is that the quality of the workpiece is improved with respect to fiber orientation and dimensional stability. Furthermore, the device according to the invention makes it possible to manufacture and demold geometries which cannot be manufactured by using a conventional device with non-directed thermal expansion behavior of the components of the device.
Expediently, the first and/or second component, which expands differently in different directions, comprises layers of different composites, in particular fiber reinforced composites with different thermal expansion coefficients. These layers are preferably arranged with respect to each other and/or connected to each other in such a manner that thermal expansion takes place in one or a plurality of preferred directions. This means connecting the layers avoids or at least minimizes a thermal expansion of the respective component in other directions. Moreover, the layers are arranged with respect to each other and/or connected to each other in such a manner that with the application of heat, the extent of the thermal expansion is determined. Hereby, the forces acting during molding on the workpiece can be optimized specifically with respect to dimensional stability and fiber orientation, provided the workpiece is manufactured from a fiber reinforced composite.
According to a further configuration, the first and/or the second component, which expands differently in different directions, comprises at least one layer of carbon fiber reinforced plastic and at least one layer of glass fiber reinforced plastic. In this connection it is particularly useful if the fibers of the at least one layer of carbon reinforced plastic and the fibers of the at least one layer of glass fiber reinforced plastic are not arranged parallel to each other. Due to the structure of the device from different (reinforcing) materials with different thermal expansion coefficients, the thermal expansion and the extent of the thermal expansion can be set specifically in different directions. It is useful here if the fibers of the at least one layer of carbon fiber reinforced plastic and the fibers of the at least one layer of glass fiber reinforced plastic are oriented with respect to each other at an angle of approximately 90°. Accordingly, the thermal expansion can be supported in one direction and can be minimized or prevented in a direction perpendicular thereto.
In a particular configuration of the present invention, the composite comprises two layers of carbon reinforced plastic between which two layers of glass fiber reinforced plastic are arranged, wherein all layers are connected to each other in a firmly bonding and/or form-locking manner. The fiber orientation in the layers of carbon fiber reinforced plastic and glass fiber reinforced plastic relative to each other can vary depending on the shape of the workpiece to be produced. A preferred orientation is 90° relative to each other.
According to a further useful configuration, the first and the second component of the device are arranged concentrically to each other, wherein the workpiece to be shaped is arranged between an outer circumferential surface of the first component and an inner circumferential surface of the second component. Here, the design and/or the material properties of the first component are selected such that the thermal expansion of said component is different in different directions and the second component has the same thermal expansion in the different directions. Accordingly, the workpiece to be produced is molded between the first and the second component without a movement in a (longitudinal) direction occurring. Expediently, for this purpose, the first and the second component are formed cylindrically, whereby the workpiece is uniformly subjected to force. The components do not necessarily have to be cylindrical, the cross-sections can also be oval, rectangular, etc.
In particular, it is provided in this particular configuration that under the effect of heat, the first component has a thermal expansion in the circumferential direction. In contrast to that, the first component has no expansion in the axial direction under the effect of heat. This ensures the molding between the first and the second component without a movement in the axial or longitudinal direction taking place.
In this concrete configuration, the second component is formed from a homogenous material or material compound. It is useful here if under the effect of heat, the second component has approximately the same thermal expansion in the circumferential direction and the axial direction. Hereby, the force required for molding the molded part can be built up between the first and the second component.
The device according to the invention is in particular used for producing a workpiece made from a composite, in particular a fiber reinforced composite.